Книга: Standard Template Library Programmer

Random Number Generator

Random Number Generator

Category: functors

Component type: concept

A Random Number Generator is a function object that can be used to generate a random sequence of integers. That is: if f is a Random Number Generator and N is a positive integer, then f(N) will return an integer less than N and greater than or equal to 0. If f is called many times with the same value of N, it will yield a sequence of numbers that is uniformly distributed [1] in the range [0, N). [2]

Unary Function

F A type that is a model of Random Number Generator.

Integer The argument type of F.

f Object of type F.

NObject of type Integer

The domain of a Random Number Generator (i.e. the set of permissible values for its argument) is the set of numbers that are greater than zero and less than some maximum value.

The range of a Random Number Generator is the set of nonnegative integers that are less than the Random Number Generator's argument.

None, except for those defined by Unary Function.

[1] Uniform distribution means that all of the numbers in the range [0, N) appear with equal frequency. Or, to put it differently, the probability for obtaining any particular value is 1/N.

[2] Random number generators are a very subtle subject: a good random number generator must satisfy many statistical properties beyond uniform distribution. See section 3.4 of Knuth for a discussion of what it means for a sequence to be random, and section 3.2 for several algorithms that may be used to write random number generators. (D. E. Knuth, The Art of Computer Programming. Volume 2: Seminumerical Algorithms, third edition. Addison-Wesley, 1998.)

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